py/mpprint: Add assertion for, and comment about, valid base values.
py/mpprint: Add assertion for, and comment about, valid base values.

Peetz0r/micropython-esp32,pozetroninc/micropython,tuc-osg/micropython,ryannathans/micropython,bvernoux/micropython,tuc-osg/micropython,SHA2017-badge/micropython-esp32,tobbad/micropython,adafruit/micropython,alex-robbins/micropython,pfalcon/micropython,trezor/micropython,MrSurly/micropython,SHA2017-badge/micropython-esp32,Peetz0r/micropython-esp32,AriZuu/micropython,henriknelson/micropython,mhoffma/micropython,MrSurly/micropython-esp32,adafruit/circuitpython,TDAbboud/micropython,hiway/micropython,blazewicz/micropython,trezor/micropython,mhoffma/micropython,henriknelson/micropython,hiway/micropython,HenrikSolver/micropython,lowRISC/micropython,MrSurly/micropython-esp32,deshipu/micropython,pozetroninc/micropython,adafruit/micropython,pozetroninc/micropython,adafruit/micropython,toolmacher/micropython,toolmacher/micropython,cwyark/micropython,dmazzella/micropython,pfalcon/micropython,blazewicz/micropython,ryannathans/micropython,PappaPeppar/micropython,HenrikSolver/micropython,PappaPeppar/micropython,tobbad/micropython,swegener/micropython,pozetroninc/micropython,Timmenem/micropython,adafruit/micropython,adafruit/circuitpython,tuc-osg/micropython,infinnovation/micropython,AriZuu/micropython,SHA2017-badge/micropython-esp32,cwyark/micropython,micropython/micropython-esp32,MrSurly/micropython,alex-robbins/micropython,tuc-osg/micropython,infinnovation/micropython,blazewicz/micropython,chrisdearman/micropython,MrSurly/micropython-esp32,ryannathans/micropython,alex-robbins/micropython,torwag/micropython,infinnovation/micropython,SHA2017-badge/micropython-esp32,pozetroninc/micropython,trezor/micropython,deshipu/micropython,infinnovation/micropython,Timmenem/micropython,selste/micropython,TDAbboud/micropython,puuu/micropython,hiway/micropython,oopy/micropython,dmazzella/micropython,henriknelson/micropython,adafruit/circuitpython,henriknelson/micropython,pramasoul/micropython,lowRISC/micropython,kerneltask/micropython,adafruit/circuitpython,toolmacher/micropython,mhoffma/micropython,micropython/micropython-esp32,AriZuu/micropython,micropython/micropython-esp32,selste/micropython,ryannathans/micropython,ryannathans/micropython,dmazzella/micropython,cwyark/micropython,swegener/micropython,Peetz0r/micropython-esp32,MrSurly/micropython,puuu/micropython,puuu/micropython,SHA2017-badge/micropython-esp32,trezor/micropython,pfalcon/micropython,oopy/micropython,mhoffma/micropython,pfalcon/micropython,MrSurly/micropython-esp32,chrisdearman/micropython,deshipu/micropython,chrisdearman/micropython,tobbad/micropython,alex-robbins/micropython,infinnovation/micropython,torwag/micropython,adafruit/micropython,selste/micropython,tobbad/micropython,henriknelson/micropython,oopy/micropython,adafruit/circuitpython,pramasoul/micropython,Peetz0r/micropython-esp32,tralamazza/micropython,lowRISC/micropython,kerneltask/micropython,hiway/micropython,torwag/micropython,Peetz0r/micropython-esp32,Timmenem/micropython,AriZuu/micropython,alex-robbins/micropython,deshipu/micropython,bvernoux/micropython,swegener/micropython,AriZuu/micropython,PappaPeppar/micropython,mhoffma/micropython,TDAbboud/micropython,cwyark/micropython,kerneltask/micropython,trezor/micropython,adafruit/circuitpython,tralamazza/micropython,pramasoul/micropython,selste/micropython,puuu/micropython,micropython/micropython-esp32,MrSurly/micropython,HenrikSolver/micropython,tralamazza/micropython,MrSurly/micropython,blazewicz/micropython,oopy/micropython,Timmenem/micropython,torwag/micropython,HenrikSolver/micropython,tralamazza/micropython,torwag/micropython,pramasoul/micropython,deshipu/micropython,chrisdearman/micropython,bvernoux/micropython,lowRISC/micropython,toolmacher/micropython,micropython/micropython-esp32,PappaPeppar/micropython,bvernoux/micropython,swegener/micropython,dmazzella/micropython,PappaPeppar/micropython,oopy/micropython,TDAbboud/micropython,pramasoul/micropython,MrSurly/micropython-esp32,lowRISC/micropython,pfalcon/micropython,TDAbboud/micropython,tobbad/micropython,bvernoux/micropython,toolmacher/micropython,selste/micropython,chrisdearman/micropython,kerneltask/micropython,Timmenem/micropython,kerneltask/micropython,swegener/micropython,blazewicz/micropython,tuc-osg/micropython,cwyark/micropython,hiway/micropython,puuu/micropython,HenrikSolver/micropython